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Similar to terrestrial networks where edge computing facilities have already been introduced to decrease the user request response delay and to reduce the backhaul bandwidth consumption, low earth orbit (LEO) satellite constellation networks can also be benefited by adopting edge computing technologies. The computation tasks generated by ground users can be offloaded to their accessing LEO satellites to enhance network QoS and user QoE. This paper focuses on modeling and simulating computation offloading at LEO constellation network edge. A one-dimensional networking model for edge computing enabled LEO constellation networks is derived, and on that basis, a Monte Carlo simulator is developed from scratch to evaluate system performance. As a case study, three different computation offloading schemes are elaborated and implemented on the simulator. Comparative evaluation experiments have been conducted and the results indicate that, in resource restricted scenarios, allowing computation offloading to the neighbors of the access satellites can considerably reduce the request blocking probability with only slightly increasing the average request response delay.

In order to meet the needs of real-time services in the low-orbit communication network, the paper draws on the related research of edge computing technology in the ground broadband network and applies it to the LEO satellite constellation communication network, sinking the processing power of the backend cloud center (CC) to the nodes close to the user terminals, thereby reducing the response delay of the task and the bandwidth consumption of the backhaul network in the LEO constellation networks. This paper proposes a sever selection strategy based on queuing theory and weighting method. For the computing offload requests submitted by frontend users, this strategy first regards the nearest accessing satellite edge computing node as the first choice to offload computing tasks; if it is not qualified, then synthetically consider various factors, such as the total energy consumption of the data transmission and calculation for the request, the load balancing among the computing nodes, and the response delay to the user, etc. These factors for candidate computing nodes are scored separately, and the all-around score is finally used to select the most suitable computation offloading node. Comprehensive simulation experiments show that, compared with another two approaches, the proposed strategy can ensure that user requests are well satisfied, and can reduce the average response delay in the range from 17% up to 34%.

The combination of edge computing and LEO satellite broadband network has the potential to provide ground users enhanced services with significantly lower latencies. This paper derives a offloading model and a user model of LEO satellite constellation networks and proposes a multi-level computation offloading scheme. This scheme designs a multilevel edge-projection pursuit (MLEPP) model and uses an optimization method to find the optimized projection direction in order to obtain the most suitable offloading choices. On the other hand, a discrete event-based Monte Carlo simulator is developed to evaluate the proposed computation offloading scheme. Comparative evaluation experiments have been conducted, and the results indicate that, in resource-restricted scenarios, using the derived multi-level offloading scheme can effectively and efficiently decrease the average request blocking probability, the average request corresponding delay, and keep the average request cost at a restricted level.

We report here the resultant effect of self-heating phenomenon on gasochromic coloration of WO 3 nanowire films covered by Pt nanoparticles (Pt-WO 3 ). Ultrafast coloration of Pt-WO 3 nanowire films on millisecond scale (less than 10 ms), which is the fastest coloration process of tungsten oxide, is observed. We have found that a unique self-heating is the major cause for speeding up the coloration process. Such self-heating occurs after several cycles of coloration and bleaching in air, without extra heater, and as a result the temperature of nanowire film can increase to above 200 °C from room temperature. The characteristics and the underlying mechanism of the self-heating have been studied in depth. It is proposed that persistent and rapid catalytic reaction between H 2 and O 2 causes heating of Pt-WO 3 nanowire. The relation between the maximum temperature of the sample reached by exposure to H 2 gas and the gas concentration can be described by a simple kinetic model, and it predicts that the down scaling of the nanowire diameter may enhance self-heating.